1. Field of the Invention
This invention relates to watercraft having two or more parallel hulls spanned by overlying deck structure and whose weight is supported in part by the surface effect of air funneled between said hulls as the watercraft moves forwardly above the surface of a body of water.
2. Description of the Prior Art
xe2x80x9cAir boatsxe2x80x9d have long been used for travel upon swamps and other shallow bodies of water. Such boats are generally catamarans having two hulls or pontoons, and equipped with aircraft type propulsion means such as an air fan propeller or jet engine located on the deck of the boat. Such design enables the air boat to function in shallow waters which would not be navigable by a vessel having a conventional immersed propeller. Examples of air boats, as described in U.S. Pat. Nos. 3,500,784; 6,148,757 further disclose the feature of capturing air between the hulls, thereby reducing the frictional drag of the water upon the boat.
Other types of air-driven vehicles include aerodynamic surface effect vessels which, with forward motion produced by aircraft type engine means, develops a ram air lifting force. Such lifting force is generally accomplished by virtue of a high velocity airstream funneled and compressed within the channel defined by the hulls, the deck and water surface. The surface effect lifting principle is capable of raising a vessel one or more feet above an underlying substantially flat surface such as the surface of a body of calm water.
An example of a vehicle employing said aerodynamic surface effect is described in U.S. Pat. No. 3,830,179 to Lippisch which concerns a vehicle for flying in close proximity to a water surface, or flat land. The Lippisch vehicle has a tail that includes a rudder as may be found on conventional aircraft, but no horizontal stabilizer as may be found at the tail of a conventional aircraft.
U.S. Pat. No. 5,464,069 to Gifford describes an air-driven vehicle which employs an aerodynamic surface effect lifting principle augmented by another lifting principle known as the hovercraft effect. In said hovercraft effect, powerful fans produce an air cushion beneath the vehicle without the necessity of forward motion, causing the vehicle to lift about an inch above a flat surface. Because the hovering capacity requires considerable fuel consumption and heavy equipment, load carrying capacity and operational range are sacrificed.
U.S. Pat. No. 3,390,655 to Quady et. al. is another form of hybrid vehicle which relies upon powerful fan jet engines to produce thrust for forward motion and, in hovercraft mode, relies upon the downwardly directed exhaust from those engines to produce an effective air cushion beneath the vehicle. The vehicle includes a tail assembly essentially like that of a conventional aircraft for steering and elevational control.
U.S. Pat. No. 5,727,495 to Reslein concerns an air propeller-driven vehicle employing an aerodynamic surface effect augmented by yet another lifting principle, namely an airfoil or wing as employed in conventional aircraft. The Reslein vehicle includes rearwardly disposed vertical air rudders for turning control, and an elevator flap mounted across the trailing edge of the airfoil for controlling the vehicle""s angle of attack in air. Although the Reslein design provides considerable lift capability, the stability of the vehicle when airborne is compromised in view of its high center of gravity, and particularly because its airfoil is positioned above the propeller.
It is accordingly an object of the present invention to provide a watercraft adapted to travel above the surface of a body of water by virtue of lift provided by an aerodynamic surface effect augmented by an airfoil effect.
It is another object of this invention to provide a watercraft as in the foregoing object having improved stability when airborne.
It is a further object of the present invention to provide a watercraft of the aforesaid nature having a multi-hulled construction and having better fuel efficiency and faster speed than conventional multi-hulled watercraft.
It is a still further object of this invention to provide a watercraft of the aforesaid nature which is propelled by aircraft-type propulsion means.
These objects and other objects and advantages of the invention will be apparent from the following description.
The above and other beneficial objects and advantages are accomplished in accordance with the present invention by an air-driven multi-hulled watercraft adapted to travel above the surface of a body of water in close proximity to said water surface, said watercraft having a vertical center plane of symmetry disposed upon a longitudinal axis extending between front and rear extremities of the watercraft and further comprising:
a) at least two identical elongated hulls equally spaced apart in parallel relationship about said plane of symmetry and adapted to buoyantly support said watercraft when at rest upon said water surface,
b) deck structure disposed between and secured to said hulls and defining with said hulls and water surface a channel through which air is compressively funneled with forward travel of said watercraft,
c) a bridge component incorporated into said deck structure and bounded in part by upper and lower surfaces and leading and trailing extremities, said bridge component having an airplane wing airfoil configuration,
d) an elongated fuselage centered within said deck structure and extending between forward and rearward extremities,
e) air-moving propulsion means associated with said deck structure behind said fuselage and having a thrust axis disposed above the upper surface of said bridge component,
f) elevons movably attached to the trailing extremity of said bridge component for elevational control of the front extremity of the watercraft, and
g) rudder means associated with the rear extremity of said watercraft for providing steering control of the watercraft when airborne and also when floating upon the water surface, whereby
h) forward motion produced by said propulsion means causes said watercraft to become airborne above the surface of a body of water by virtue of both the aerodynamic surface effect produced by air passage through said channel and by the lifting effect produced by the airfoil-shaped bridge component, said watercraft having stability in said airborne state by virtue of the critically selected features of construction and the controlling effects of said elevons and rudder means.